PROJECT SUMMARY/ABSTRACT This K01 will provide the principal investigator, Dr. Karey O?Hara, with training and mentored research experiences that will support her transition to an independent intervention scientist specializing in the development of optimized preventive programs for children exposed to uncontrollable stressors that are theory-driven, effective, and scalable. The focus of this K01 is on children?s exposure to interparental conflict after divorce. The training plan provides (1) skills in intervention development and evaluation, including the multiphase optimization strategy (MOST)20 framework, ecological momentary assessment (EMA), theory-based intervention development, and randomized controlled trials (RCTs), (2) experience in applying user-centered design (UCD)8,9 strategies to encourage implementation success. These training goals will be accomplished through workshops (e.g., MOST, UCD, EMA) and coursework (e.g., seminars on experimental and quasi-experimental design, web-based program design, theory-based programs for divorce), as well as didactic instruction (i.e., directed readings), hands-on training (i.e., large-scale RCT, analysis of existing EMA data), and mentored research experiences. The proposed K01 training and research activities will be executed at Arizona State University?s (ASU?s) Department of Psychology and Research and Education Advancing Children?s Health (REACH) Institute. Primary mentorship will be provided by Dr. Sharlene Wolchik (ASU; expert in children?s mental health and parental divorce, intervention development and evaluation) and co-mentorship will be provided by Dr. Irwin Sandler (ASU; expert in children?s stress and coping, parental divorce, intervention development and evaluation) and Dr. Stephen West (ASU; expert in factorial design, causal inference, longitudinal analysis, program evaluation). In addition, Dr. O?Hara will receive training from Dr. Linda Collins (Penn State; developer of MOST), Dr. E. Mark Cummings (University of Notre Dame; expert in interparental conflict), Dr. Aaron Lyon (University of Washington; expert in UCD strategies), and Dr. Harry Reis (University of Rochester; expert in EMA). The overarching objective of the proposed projects is to develop an optimized intervention for children exposed to high post-divorce interparental conflict, as this is a leading risk factor for mental health problems in children who experience divorce. To achieve Aim 1, I will use UCD strategies (surveys, focus groups, quantitative measures, user-testing) to ascertain information from potential end-users on needs, preferences, usability, and satisfaction. To achieve Aim 2, I will apply MOST and conduct a factorial optimization trial to isolate effects of web-based coping intervention components. This research aligns with the NIMH ?experimental therapeutics? approach to intervention development and evaluation.